KSeF (Poland's national e-invoicing system)
KSeF is the Polish Ministry of Finance platform through which structured XML invoices pass. An invoice issued in KSeF gets an identifying number and is available to both sides of the transaction without emailing a PDF.
For a company this means two changes. On the sales side the invoice has to be created in a structured format and sent to KSeF, usually straight from the system that issues it. On the purchase side, cost invoices can be pulled from KSeF automatically instead of waiting for the supplier to send them and for someone to re-key them.
The purchase side is the more interesting one operationally. Because the invoice arrives as data rather than a PDF, it can be matched automatically against the order and the delivery, and a difference in price or quantity can be shown to whoever approves it. The step of re-keying and hunting for the matching order disappears.
KSeF does not force an ERP replacement. An integration is usually enough: the company's system sends and fetches documents through the KSeF API, and the rest of the process stays where it was. The trouble starts when invoices are created outside the system, for example in a spreadsheet or a separate invoicing tool.
A separate matter is the documents that never reach KSeF: receipts, invoices from foreign suppliers, credit notes, contracts. Those still arrive by email and scan, so a company needs one document flow for both streams rather than two parallel ones.